This invention relates in general to milling machines and in particular to three-axis milling machines.
The technology associated with machine tools is extensive and diverse. Known in the art are one, two and three-axis machines, some of which grind or mill, others of which drill or bore. The types of attachments and options are almost as varied as the number of different machines. The following list of patents gives a brief indication of some of these various types of machines and features:
______________________________________ U.S. Pat. No. Patentee Issue Date ______________________________________ 3,555,963 Evans 1/19/71 3,617,142 DeWane 11/02/71 3,157,283 Maass et al. 11/17/64 2,963,057 Morse 12/06/60 2,883,890 Fink et al. 4/28/59 2,365,068 Gerbig 12/12/44 ______________________________________
Evans discloses a multiple spindle transfer machine having a removable spindle tool holder and in which a single drive motor is used to drive each spindle through a gearing arrangement. The entire tool head moves in a vertical direction by means of a worm gear and pinion drive using guides and slides on each side thereof.
DeWane also discloses a vertically movable head in which a DC drive motor is geared to drive the tool spindle. The head is mounted to the structure by a slideway arrangement and movement occurs by use of a counterbalancing weight and pulley arrangement.
Each of these patents disclose conventional slideway or guide means for controlling the alignment of the vertical travel. Such means require accurate machining, lubrication and major overhaul by replacement or remachining when they become worn. Furthermore, each of these two patents utilize gearing to transfer the rotary motion of the motor shaft to drive the tool spindle.
The remaining four patents are listed as being of only general applicability to conventional three-axis machine tools. Each of these patents disclose a particular unique application or feature which might be associated with a particular machine tool. Maass et al. discloses mandrel-changing means for a tube-extrusion press. Morse discloses a multi-purpose machine tool with means for varying the spindle position. Fink et al. discloses an automatic drill changer for chucks. Gerbig discloses a machine for reconditioning insert-type connecting rods.
The following list of patents deals with drive units and mechanisms which have hollow shaft motors or the like:
______________________________________ U.S. Pat. No. Patentee Issue Date ______________________________________ 1,636,560 Hall 7/19/27 1,967,045 Wehmeyer 7/17/34 2,500,175 Guthrie 3/14/50 2,571,267 Ljunggren 10/16/51 2,703,847 Kalikow 3/08/55 2,772,546 Barrows 12/04/56 3,854,063 Bergman 12/10/74 3,987,322 Bourgain et al. 10/19/76 2,714,866 Pleuger et al. 8/09/55 ______________________________________
The Hall patent discloses a hollow shaft motor employed for a valve seat grinder in which the hollow shaft is used to accommodate a pilot stem.
The Wehmeyer patent relates to machine tools only in that it includes a chuck-operating motor which is mounted on a lathe spindle.
The Guthrie patent discloses a flexible coupling concept associated with direct-current, reversible step motors.
The Ljunggren patent discloses a thread-spinning spindle having a hollow shaft motor drive for the blade which drives the spool through a flexible coupling.
The remaining patents are of only general applicability in that they do not relate to conventional drive motors for use with three-axis machine tools. In addition, none of these listed patents involves the concept of the coaxial coupling of a conventional solid output shaft of a motor to a hollow tool chucking spindle. This particular coaxial coupling concept provides the advantages of individually replaceable parts, without having to replace the entire assembly, and the ability to use standard, commercially available motors.
Kalikow discloses a driving mechanism for starter-generators. Barrows discloses a flexible drive concept for absorbing or reducing torsional vibration. Bergman discloses an arrangement for directly coupling an electric motor to the shaft of driven equipment which permits a small misalignment. Bourgain et al. discloses a coupling device for use between an electric motor and an element which is driven at high speeds and suspended from a connecting rod. Pleuger et al. discloses a device for propelling a ship and includes an electric motor.
U.S. Pat. No. 2,028,727 issued Jan. 21, 1936 to Perry et al. discloses a particular construction of machine tools wherein the tools are distinctly segregated into a number of major structural units. One aspect of this segregation is that the tool head is readily detachable from a saddle member and the saddle member is readily detachable from the vertical support column of the subject machine tool. Although the saddle member is slidable on the ways of the vertical column, this design in no way solves the problems of machining accuracy, lubrication and wear associated with such slide and guide arrangements as previously discussed.
The following list of patents deals with tool knock-out devices associated with machine tools:
______________________________________ U.S. Pat. No. Patentee Issue Date ______________________________________ 3,673,918 Zankl 7/04/72 3,220,313 Schroeder 11/30/65 3,757,637 Eich et al. 9/11/73 3,520,228 Wohlfeil 7/14/70 2,242,475 Misuraca 5/20/41 ______________________________________
Zankl discloses an adjustable vibration dampener for a slidable machine tool member such as a spindle head. The dampening means are particularly adapted to selectively and adjustably compensate for vibration due to the anti-friction support means in such a manner as to increase the quality and depth of a particular metal-cutting operation by overcoming the tendency to vibration. Disclosed as part of this device is the use of belleville spring washers in combination with a circular bearing shoe which is resiliently urged axially inward to exert a predetermined frictional pressure against a vertical way.
Schroeder discloses a machine tool power drawbolt mechanism arranged within a hollow spindle member of a machine tool. The threaded engagement between the drawbolt and the tool holder represents a somewhat conventional construction but is not suitable for a quick release, tool knock-out arrangement.
Eich et al. discloses a device for the automatic replacement and adjustment of tool carriers, such as angular milling heads on a milling support on a machine tool. This device is of interest for its showing of a drawbar arrangement which is axially slidable and rotatably mounted in the milling spindle. This design also represents a somewhat conventional drawbar or drawbolt construction wherein the drawbar is externally threaded and screwed into the tool shank before the actual axial movement of the drawbar takes place by means of the motor.
Wohlfeil discloses a machine tool control system with control circuits for arresting rotation of a machine tool spindle in a fixed rotary orientation position. The system includes a drawbolt which is used to secure work tools in the spindle and is rotatable relative to the spindle to release one work tool and grip another. Also included is a control circuit for sensing any failure of the drawbolt to properly rotate relative to the spindle.
Misuraca discloses a motorized hand tool such as that associated with small grinding wheels, abrasive elements, drills and electric erasers. This device is listed for its showing of a hollow spindle and a release mechanism for the particular element held in the hollow spindle.